<?php

//PHP -S localhost:80
//?email=(bogus@example.or g)

$sanitised_a = filter_input(INPUT_GET, 'email', FILTER_VALIDATE_EMAIL);
var_dump($sanitised_a); // 当url为 GET /4.filter_input_validate.php?email=bogus@example.or g 时该语句输出 bool(false)
